Devils Postpile National Monument

Devils Postpile National Monument
IUCN Category III (Natural Monument)
Location	Madera County, California, USA
Nearest city	Mammoth Lakes, CA
Coordinates	37°37′28″N 119°5′4″W / 37.62444°N 119.08444°W / 37.62444; -119.08444Coordinates: 37°37′28″N 119°5′4″W / 37.62444°N 119.08444°W / 37.62444; -119.08444
Area	798 acres (323 ha)
Established	July 6, 1911
Visitors	114,788 (in 2004)
Governing body	National Park Service

Rainbow fall at Devils Postpile National Monument

The longer fragments of basalt at the base of the cliff are much larger than a person.

Devils Postpile National Monument is located near Mammoth Mountain in extreme northeastern Madera County in eastern California. It was established in 1911, and protects Devils Postpile, an unusual formation of columnar basalt.

Geography

Devils Postpile National Monument contains 798 acres (3.23 km²) and includes two main tourist attractions: Devils Postpile (a columnar basalt formation); and Rainbow Falls, a waterfall on the Middle Fork of the San Joaquin River. In addition, the John Muir Trail and Pacific Crest Trail merge into one trail as they pass through the monument.^[1]

History

Devils Postpile National Monument was once part of Yosemite National Park, but discovery of gold in 1905 near Mammoth Lakes prompted a boundary change that left the Postpile on adjacent public land.^{[citation needed]} A proposal to build a hydroelectric dam later called for blasting the Postpile into the river. Influential Californians, including Walter L. Huber, persuaded the federal government to stop the demolition and in 1911, President William Howard Taft made the area into a United States National Monument.

Flora and fauna

The flora and fauna at Devils Postpile are typical of the Sierra Nevada.^[2] The Monument contains animals and plants such as black bears, pine martens, mule deer, coyotes,^[3] quaking aspen, black cottonwood, alder, and willows,^[4] as well as many wildflowers, such as cinquefoil and alpine shooting star.^[5] Dark-eyed juncos and white-crowned sparrows are common in the summer.^[5]

Devils Postpile

Devils Postpile itself is a dark cliff of columnar basalt created by a lava flow sometime between less than 100,000 years ago (according to current potassium-argon dating) to 700,000 years ago (according to other dating methods). The source of the lava is thought to have been somewhere near Upper Soda Springs campground at the north end of Pumice Flat on the floor of the Middle Fork of the San Joaquin River, from where it flowed to the site of the Postpile, was impounded by a moraine, and reached a thickness of 400 feet (newer estimate) to 600 feet (older estimate). In any event, the lava that now makes up the Postpile was near the bottom of this mass.

Because of its great thickness, much of the mass of pooled lava cooled slowly and evenly, which is why the columns are so long and so symmetrical. Columnar jointing occurs when certain types of lava cool; the joints develop when the lava contracts during the cooling process.

A glacier later removed much of this mass of rock and left a nicely polished surface on top of the Postpile with very noticeable glacial striations and glacial polish.

The Postpile's columns average 2 feet (0.61 m) in diameter, the largest being 3.5 feet (1.1 m), and many are up to 60 feet (18 m) long. Together they look like tall posts stacked in a pile, hence the feature's name. If the lava had cooled perfectly evenly, all of the columns would be expected to be hexagonal, but some of the columns have different polygonal cross-sections due to variations in cooling. A survey of 400 of the Postpile's columns found that 44.5% were 6-sided, 37.5% 5-sided, 9.5% 4-sided, 8.0% 7-sided, and 0.5% 3-sided.^[6] Compared with other examples of columnar jointing, the Postpile has more hexagonal columns. Another feature that places the Postpile in a special category is the lack of horizontal jointing.

Several stones from the Devil's Postpile can be seen at the entrance to the United States Geological Survey headquarters lot in Reston, Virginia.

Similar structures

a fragment of columnar basalt that has fallen after separating from the main mass of the Devils Postpile

Although the basaltic columns are impressive, they are not unique. Basalt columns are a common volcanic feature, and they occur on many scales (faster cooling produces smaller columns). Other notable sites include Giant's Causeway in Northern Ireland, Fingal's Cave in Scotland, Titan's Piazza of the Mount Holyoke Range in Massachusetts, the Garni Gorge in Armenia, the Cyclopean Isles near Sicily, Sheepeater Cliff at Yellowstone National Park in Wyoming, Prismas Basálticos in Huasca de Ocampo, Mexico, the "Organ Pipes" formation on Mount Cargill in New Zealand, Gilbert Hill in Mumbai, Organ Pipes National Park in Australia and the "Columnar Cape" (Russian: Mis Stolbchaty) on Kunashir Island, the southernmost of the Kuril Islands. Columnar basalt can also be seen in a high desert dry river falls area just north of Lajitas, Texas. The much more massive Devils Tower National Monument in Wyoming is superficially similar but consists of a phonolite porphyry, formed by the intrusion of igneous rock.^[7]

See also

• Gilbert Hill
• Little Devils Postpile
• Category: Rock formations in California

Bibliography

• Roadside Geology of Northern and Central California, Alt, Hyndman (Mountain Press Publishing Company, Missoula; 2000) ISBN 0-87842-409-1

References

1. ^ "Plan Your Visit". Devils Postpile. National Park Service. http://www.nps.gov/depo/planyourvisit/brochures.htm. Retrieved 2011-06-25. 
2. ^  This article incorporates public domain material from the National Park Service document "Devils Postpile: Nature & Science" (retrieved on 2010-04-23).
3. ^ "Animals". Devils Postpile. National Park Service. http://www.nps.gov/depo/naturescience/animals.htm. Retrieved 2010-04-23. 
4. ^ "Plants". Devils Postpile. National Park Service. http://www.nps.gov/depo/naturescience/plants.htm. Retrieved 2010-04-23. 
5. ^ ^{a b} Grossi, Mark. "Devils Postpile National Monument". Longstreet Highroad Guide to the California Sierra Nevada. Sherpa Guides. http://www.sherpaguides.com/california/mountains/eastern_sierra/devils_postpile_national_monument.html. 
6. ^ "Devils Postpile National Park Geologic Story". USGS/National Park Service. January 2, 2000. http://www2.nature.nps.gov/geology/usgsnps/depo/dpgeol5.html. 
7. ^ Bassett, WA (1961). "Potassium-Argon Age of Devils Tower, Wyoming". Science 134 (3487): 1373–3. doi:10.1126/science.134.3487.1373. 

External links

Malheur Butte

• Official NPS Site
• The Devil's Post Pile. Popular Science monthly. Feb 1916,. p. 178. http://books.google.com/books?id=iSYDAAAAMBAJ&printsec=frontcover&cad=0_2#PPA178,M1.